First Report on the Rapid Detection and Identification of Methicillin-Resistant Staphylococcus aureus (MRSA) in Viable but Non-culturable (VBNC) Under Food Storage Conditions.

Aifen Ou,Yanrui Ye,Yimin Zou,Yanxiong Mao,Tengyi Huang,Lei Yuan,Kan Wang,Ling Chen

doi:10.3389/fmicb.2020.615875

Abstract

Formation of viable but non-culturable (VBNC) status in methicillin-resistant Staphylococcus aureus (MRSA) has never been reported, and it poses a significant concern for food safety. Thus, this study aimed to firstly develop a rapid, cost-effective, and efficient testing method to detect and differentiate MRSA strains in the VBNC state and further apply this in real food samples. Two targets were selected for detection of MRSA and toxin, and rapid isothermal amplification detection assays were developed based on cross-priming amplification methodology. VBNC formation was performed for MRSA strain in both pure culture and in artificially contaminated samples, then propidium monoazide (PMA) treatment was further conducted. Development, optimization, and evaluation of PMA-crossing priming amplification (CPA) were further performed on detection of MRSA in the VBNC state. Finally, application of PMA-CPA was further applied for detection on MRSA in the VBNC state in contaminated food samples. As concluded in this study, formation of the VBNC state in MRSA strains has been verified, then two PMA-CPA assays have been developed and applied to detect MRSA in the VBNC state from pure culture and food samples.

Highlights

Food safety has been found to be a leading concern for public health worldwide, and food pathogens remain the major factor as a causative for foodborne diseases (Deng et al, 2015a)
To induce the viable but non-culturable (VBNC) state of methicillin-resistant Staphylococcus aureus (MRSA), the culture was diluted to the final concentration at 108 colonyforming unit (CFU)/ml with food homogenate (Cantonese pastry, steamed bread, rice flour; Guangzhou Restaurant, Guangzhou, China)
They were stored at −20◦C to induce the VBNC state for further use of propidium monoazide (PMA)-crossing priming amplification (CPA)

Summary

Introduction

Food safety has been found to be a leading concern for public health worldwide, and food pathogens remain the major factor as a causative for foodborne diseases (Deng et al, 2015a). Considered to be a major nosocomial pathogen, MRSA has been found to be an important foodborne pathogen in recent years. Aside from its biofilm formation capability and known to be a typical biofilm former, MRSA could produce different types of toxins and is responsible for various human diseases (Kadariya et al, 2014; Miao et al, 2017a,b). A number of foodborne outbreaks were reported to be caused by MRSA (Voss et al, 2005; Xu et al, 2017, 2019)

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Conclusion